1. Field of the Invention
The present invention relates generally to optical recording systems having read-after-write features.
2. Background Information
In many data recording systems a method and/or system for reading the data immediately after it is written is implemented so that the accuracy of the recorded data can be ascertained. In linear magnetic tape systems for example, the read/write head array is duplicated in close proximity to enable write verification with the tape moving in either direction. In optical disc systems the read-after-write function is usually implemented by a consecutive turn of the disc. The read-after-write (RAW) function is considered necessary for a viable recorder, and it is therefore desirable to implement a near simultaneous read after write for linear optical tape systems.
In systems using multiple optical beam writing, the data is typically written in a defined block size down the tape and across multiple write channels. Tape surface errors prevent perfect error free recording and an error correcting coding (ECC) scheme is implemented to remove the effects of such errors on the recorded data. With an immediate RAW it is possible for the system to evaluate to what extent the ECC is being utilized to correct the written errors back to an acceptable level. If the written data cannot be immediately retrieved with sufficient fidelity via the ECC circuits, the optical tape system is configured to re-write the unrecoverable data block. Block rewrites are implemented until either accurate data is recovered or until a pre-set number of rewrites have failed, at which point system failure is indicated. The degree to which the ECC is being utilized to correct the recovered data can also be monitored so that data can be retrieved and duplicated before insufficient ECC is available and the data to becomes unrecoverable.
For simultaneous multiple beam writing using, for example, an array of 4xc3x978 beams in an equally spaced rectangular matrix, it is desirable to read each data bit shortly after it is written. This requires a trailing matrix of 4xc3x978 optical beams at the reduced read light intensity, regardless of the direction in which the recording media is traveling. In systems using arrays of laser diodes, this requires a second array of laser diodes similar to the write array, with the write and read functions being alternated.
The present invention provides an optical apparatus including a mirror for an optical recording system. The mirror is coupled to an adjustable base which is moveably coupled to a fixed support. The adjustable base is adjustable to orient the mirror in at least a first position to reflect reading light beams of the optical recording system onto a recording medium.
The present invention also provides a method of performing a read-after-write operation in an optical recording system. The method includes adjusting a mirror to a first angled position or a second angled position, directing an unmodulated light beam from a light source to the mirror to reflect the light beam onto a lens, and using the lens to focus the unmodulated light beam on a recording medium to read a written track on the recording medium.
Additional features and benefits of the present invention will become apparent upon review of the following description.